Thank you for your question.

While your pre-emergent herbicide appears to have been effective for crabgrass, the poa annua was germinating last August/September. Your pre emergent application this spring would not have affected the poa annua.

Here is a good article on poa annua: https://hgic.clemson.edu/factsheet/annual-bluegrass-control/

There are herbicides, like Tenacity that are somewhat effective on poa annua: https://archive.lib.msu.edu/tic/golfd/article/2012oct33.pdf

While it takes several applications and some specific weather conditions, the MSU test dd show very effective reduction in poa annua plant density.

As far as mowing is concerned, mowing frequently and bagging is most effective, because the seeds on poa annua are viable.

Your best treatment plan is to:

1. Mow frequently and bag the clippings
2. Apply Tenacity to knock down the density of poa annua
3. Apply pre-emergent herbicides (different in each application per the Clemson article) in August and September.

Now to address the overseeding. This presents other challenges. Your best choice is to overseed in the spring. You can use a crabgrass pre-emergent that is safe for seeding and then overseed as soon as the soil and weather is warm enough. Or, you can overseed at the correct time in the spring and use a post emergent crabgrass herbicide later in the summer to address any crabgrass that germinates. Unfortunately, fall overseeding will not be viable as long as you need to treat the poa annua with a pre-emergent herbicide. The pre-emergent for the poa annua will also prevent grass seed from germinating.

Here is some information on post-emergent crabgrass treatment: https://www.canr.msu.edu/news/controlling_crabgrass_after_it_emerges

Hope this helps.

Hello George,

If you cannot apply the Group 2 Pre-emergent because of having tall fescue, You will need to apply the Group 1 herbicide only and hope that you do not experience herbicide tolerance.